This invention relates to electrical equipment for controlling a record/playback device to operate in one of at least three different modes in response to control signals delivered along a single conductor. The invention is particularly useful in controlling a record/playback device that provides a playback or retrieval operation, a record operation, and a reverse or rewind operation in response to signals produced with separate switches and communicated on a single signal conductor. A recording device of this character is also referred to herein simply as a "recorder," and the invention is described with particular reference to such a recorder. Features of the invention, however, may be used to advantage in controlling other electrical devices.
Audio records are commonly available which use magnetic recording tape and which can play back recorded information and record new information. Also, recorders can repeat playback by briefly rewinding the recording tape and automatically resuming playback. Alternatively, the "backing up" along the recording tape that the rewind operation produces can be followed by a record operation, to record new information at the tape section just rewound past the recording head. Recorders of this kind are conventionally controlled with any of numerous schemes, including the typical use of separately-wired independent switches for each operating function.
For remote cable control of a recorder in response, for example, to switches on a hand-held control box, it is often desirable to minimize the number of cable conductors. A small cable can be stored compactly and is flexible and hence easy to deploy. A cable feeding into a recorder typically has a separate conductor for each remote microphone, of which there are at least two for stereophonic recording. Additional separate conductors for each control function can result in the cable being undesirably bulky, heavy and stiff.
Similar problems can arise with a visual recorder such as a combined camera and projector. Here the separate operating functions typically include record, project and rewind. Again, remote control via a cable having few conductors may be desirable.
Accordingly, it is an object of this invention to provide electrical equipment for providing remote cable control of multiple functions of a record/playback device with a single signal conductor.
A more particular object is to provide electrical equipment for the remote cable control of record, playback and rewind operations, as signalled from separate control switches, on a single signal conductor.
It is a further object that the foregoing electrical equipment normally assume a condition that protects the recording medium from inadvertent recording or erasure.
Other objects are that the equipment operate with high reliability and be low in cost.
These and other objects of the invention are in part described more fully below and in part will be obvious to those skilled in the art from the following description.